The present invention relates to a mobile communication system which communicates between a base station and a plurality of mobile stations using the TDMA method, and particularly, to a mobile communication system which is able to reduce the electrical power consumed by a mobile station which employs the TDMA method to receive data signals.
In the conventional technology, when a data signal for a mobile station is generated, a base station that uses the TDMA method for communication searches for a vacant slot in a TDMA channels, and transmits the data signal using the vacant slot immediately after generation of the data signal. Meanwhile, a mobile station monitors all slots, and receives the data signal in the slot if that data signal is addressed to that station.
In this case, however, in order to determine whether a data signal is addressed to itself, the mobile station must demodulate a data signal in every received slot and read a mobile identifier which is contained in each slot. Electrical power is therefore consumed by the mobile station in carrying out the above mentioned procedures. At the same time, it is necessary to extend the signal waiting time of the mobile station, and to reduce the size of the mobile station""s battery. In order to meet these requirements, it is thus desirable to reduce as much as possible the electrical power used in the data signal detection.
The present invention was developed in consideration of the above circumstances, and has as its objective the provision of a mobile communication system wherein it is possible to reduce the electrical power consumed by the mobile station during the signal reception waiting period, by observing only the starting slot on a TDMA radio channel.
(1) A mobile communication system that transmits data signal from base station to a plurality of mobile stations by using TDMA radio channel that consists of a plurality of slots; wherein
said base station consists of
a generating means for generating a head slot having a mobile station identifier which indicates a mobile station for transmission and continuous slots having a least part of said data signal,
a transmission means for transmitting said head slot with starting slot which locates at predetermined position each of said a plurality of mobile stations, on said TDMA radio channel, and
a transmission for transmitting said continuous slot with slot which continues said starting slot,
each of said mobile stations consists of
a observation means for observing said starting slot,
a judging means for judging said mobile station identifier when said starting slot is a head slot,
a receiving means for receiving said continuous slot when said mobile station identifier indicates oneself.
Therefore, according to the present invention, a mobile station monitors only a starting slot, so that it is possible to reduce the electrical power of the battery consumed by the mobile station to be shorten the operating time of a receiving apparatus, in comparison with in case where the mobile station monitors all slots.
(2) Said base station further consists of a transmission means for transmitting vacant slot which does not contain said data signal when there is no said data signal,
said mobile station further consists of a stopping means for stopping a receiving operation until next of said starting slot when said starting slot is said vacant slot or said continuous slot.
Therefore, according to the present invention, when the received slot is a vacant slot or when received slot is a signal slot addressed to other mobile station, the mobile station stops reception of signal, so that it is possible to be shorten a delay time of the signal by transmitting continuously a plurality of signals.
(3) Said base station further consists of a generating means for generating synchronous words of various kinds which is for synchronizing to said slots,
a transmission means for transmitting a synchronous word selected from said synchronous words of various kinds to contain in said slots, on the basis of the information which indicates whether the monitored slot is said starting slot or not, said mobile stations further consists of a judging whether said slot is said starting slot or not, on the basis of the kind of said synchronous word.
Therefore, according to the present invention, the mobile station can judge the position of the starting slot at the same time as synchronizing of slots.
(4) Base station sets a common starting slot at a predetermined position on said TDMA radio channel, and farther consists of a generating means for a continuous slot having mobile station identifiers which indicate said plurality of mobile stations and at least a part of said data signal when said base station transmits common data signal for a plurality of mobile stations,
a transmission means for transmitting said starting slot with said common starting slot,
a transmission means for transmitting said continuous slot with said slots which follows said common starting slot,
said mobile station further consists of a monitoring means for monitoring said common starting slot, in addition to said starting slot which determined for every mobile station,
a recognition means for recognizing said mobile station identifier when said common starting slot is said starting slot, a receiving means for receiving said continuous slot if there is a mobile station identifier which indicates itself among said mobile station identifiers.
Therefore, according to the present invention, it is possible to reduce the electrical power of the battery consumed by the mobile station, and to ensure signal transmission addressed to each mobile station by arranging to disperse slot of each mobile station. Furthermore, it is possible to shorten a delay time wherein a common signal is transmitted to a plurality of mobile stations by set a common starting slot that a plurality of mobile stations begin reception commonly, in comparison with the case where an individual slot is used each mobile station. In addition, it is possible to improve the using efficiency of the TDMA radio channel by that over-lapped signal does not transmit.
(5) Said base station further consists of a transmission means for transmitting a informing signal indicating a position of said starting slot for each of mobile stations,
said mobile station further consists of a starting means for starting a receiving operation from said starting slot which is indicated by said information signal.
Therefore, according to the present invention, it is possible to inform immediately presence of data signal to the mobile station, in comparison with the case where data signals are transmitted successively to one or more mobile stations, by informing presence of data signal to one or more mobile stations with the informing signal.
(6) Said mobile station further consists of a transmission means for transmitting a receiving mode which indicates whether it monitors all slots or it monitors only starting slot,
an observing means for observing said slot by the receiving mode which is transmitted by said transmission means,
said base station further consists of a receiving means for receiving said receiving mode,
a transmission means for transmitting said data signal to a mobile station which transmits said receiving mode from a slot immediately after that said data signal is generated, when said receiving mode indicates to monitor said all slots, a transmission means for transmitting said data signal for a mobile station which transmitted said receiving mode from said starting slot when said receiving mode indicates that said mobile station monitors only said starting slot.
Therefore, according to the present invention, it is possible to switch a transmission mode by request from the mobile station in the base station. Furthermore, it is possible to immediately transmit data signal by switching a succession transmission mode, in the case where the traffic is large or the permitted transmission delay is small. In addition, it is possible to change a transmission procedure to the intermittent transmission mode at the start of communication or during communication, according to the limit of the battery consumption in the mobile station.
(7) Said base station further consists of a transmission means for transmitting a slot designating signal which contains information indicating a position of said starting slot,
said mobile station further consists of a receiving means for receiving said slot designating signal, a judgment means for judging a position of said starting slot based on said slot designating signal.
Therefore, according to the present invention, it is possible to determine the arrangement of the starting slot and the common starting slot, according to the conditions.